You can unite with your roommate and try to hint at this roommate with particularly poor hygiene habits, reminding him that he has something to wash and change. Try to tell him that there is something wrong with his hygiene habits in a way that doesn't hurt his face, and let him pay attention to it himself. If one of you tells him directly in words, try not to make him think that you hate him or dislike him. Tell him that if he gets rid of his bad habits, everyone will still be good roommates.
You should urge and help him to correct it. For example, when it's time to wash clothes or take a shower, you should call him together and tell him that if he doesn't clean regularly, he will easily get sick. It's also very pleasant for everyone to wash together for nothing.
Facing the problem of cleaning public health, if he can't clean his own health, then he can't clean public health, so I suggest you make a plan to clean public health that everyone agrees to implement.
In the plan, specify in detail the part that everyone should be responsible for and the cleaning time. If possible, set the same time for everyone to clean together once a week. If everyone agrees, then this roommate with poor hygiene habits will also agree because of face problems.
When you make a plan, you should urge everyone to implement it. If he didn't do it and didn't clean himself, then you can also make corresponding punishment measures and punish him for cleaning one more day.
If he continues to teach, even his bad hygiene habits will affect your normal life. Then you should collectively persuade him to move out of this dormitory or complain to other teachers about him.